Cameras that used film needed black bodies to better protect the sensitized film, against stray light Since pretty much all the pros were using black colored bodies, black became synonymous with "professional" .... This just continued on to the digital world ... also, black generally is considered "professional" even in other fields e.g. wearing a black suit is generally considered "serious and professional" ... but I don't think any technical aspect stops manufacturers from producing colored DSLR's, other than the fact that most people will not opt for colored DSLRs ... I know I would never buy a white, pink, green etc DSLR bodies ... so I suppose it is just a marketing decision now.

When you are trying to look at a limited scene within a broader field, having the "surround" (camera body) darker than the target scene( viewfinder, LCD, etc.) is much easier on the eye than having the scene surrounded with a glaring bright field.

A glossy-finish pure white makes just such a reflective glaring border around what you are trying to view with the least possible interference to your vision.

If you are an Indian, (like me who has worked in Delhi, Mumbai, Chennai, Hyderabad, Bangaluru & Calcutta), trust me you will know ... coz there are a lot of people, in those cities, urinating on the walls.